Oh great, let's all bash the instructors again.
Just let it go, plz.
I don't care about any "official credentials". I don't care if the coach taught Elvis Presley or the Pope. I don't even care if they taught any famous players, because, usually what happens is that a player is 95% developed, then a coach swoops in and tries to take credit for the whole thing. We have one of these vulture coaches in Europe, quite famous too. Won't name him.
I care about the following:
Does the coach teach sound techniques:
1. Four point contact
2. Stroke with pauses
3. Proper stroke timing
4. Proper breaking technique, with body rise and everything.
Does the coach teach proper strategies:
1. High percentage safes, with low hit probability
2. Proper patterns
3. Use of side spin as a tool to get out in a high percentage manner
Can the coach demonstrate what he teaches:
1. Does he play at a high level, or did so in the past?
2. If he sets up a drill, can he complete it?
3. Is his stroke and stance textbook, or if not, is there a good reason why?
Red flags:
1. Advocates center ball as a way to play professional speed
2. Doesn't teach break properly
3. Goes against the established practises of pros, without being able to demonstrate that his way is superior.
4. Overly hung up on basic level drills
5. Lots of physics and maths, few balls in the pocket...
6. Cookie cutter approach
If a coach passes these hurdles, then I don't care about any sort of certification. If they don't pass, I won't hire them. Someone else might, and that's perfectly fine. I've picked up lots of tips from guys who can't play a lick. I won't hire them to teach me, though.